Carbon nanotubes (CNTs) offer significant advantages over other materials in that they possess substantially higher strength-to-weight ratios and superior mechanical properties. Since their discovery, there have been numerous disclosures in the art pertaining to synthesis and morphology of CNTs, including methods for controlling tubule growth during their formation. Efforts to realize many potential applications envisaged for CNTs include their modification to produce new one-dimensional nanoscale materials, introduction of foreign materials by capillary and electric arc methods, and conversion into nanoscale carbide materials such as silicon carbide (SiC), tungsten carbide (WC), etc. by reacting them with the corresponding metal-oxides.
Electrically conductive polymers (ECPs) have been studied extensively over the past two decades. Simple ECPs, typically polypyrrole (PPy), polyaniline (PAni), polythiophene (PTh) and polyacetylenes (PA), can be prepared either chemically or electrochemically. Besides having relatively high conductivity in oxidized and ion-doped states, simple ECPs also show interesting physicochemical properties that are potentially useful in batteries, energy storage cells, sensors, capacitors, light-emitting diodes, and electrochromic displays. For many of these applications, especially in batteries, a high charge capacity is required. In order to increase the charge capacity of a polymer battery, the doping charge of the polymer film must be increased. This goal can be practically achieved by increasing the film thickness of ECPs. However, it has been found that the electrical performance of conducting polymers is strongly influenced by the kinetics of the doping-undoping process of ions within the film. For a conventional PPy electrode, increasing the film thickness causes deterioration of electrodic performance (e.g., charging-discharging rate) due to the long ion diffusion time and migration length in the thick film. It has been shown that a porous PPy structure with large specific surface area is a prerequisite for high-power applications due to the high charging and discharging rates. Films of nitrile-butadiene rubber (NBR) when used as a template for oriented growth of PPy in NBR matrix-grown PPy electrodes possess an open, porous structure with high surface area admitting a faster anion doping process than ordinary PPy electrodes.
Methods for coating metals and organic conductive polymers on the surface of CNTs to produce one-dimensional nanoscale composites can be used in battery, magnetic storage, fuel cell, and composite applications, since they are extremely porous substrates with large surface area and possess good mechanical properties. The use of carbon substrates for improving mechanical properties of electrically conducting polymers is known. This method however, requires greater than 25% (by weight) of polypyrrole to be deposited on the fibers in order to achieve a continues phase that is critical for electrical conductance. Efforts to use CNTs as viable substrates for electrically conducting materials disclosed in the art have been largely limited to fabrication of one-dimensional nanoscale composites of CNTs containing polypyrrole (PPy), nickel (Ni), Cobalt (Co), titanium (Ti), tungsten (W), palladium (Pd), gold (Au), aluminum (Al) and iron (Fe). Such composites, which are typically obtained by chemical synthesis, physical vapor deposition and electron-beam evaporation methods however, do not provide coating uniformity on the CNT surface, which is critical for their application in energy storage devices. This limitation is mainly attributable to tangling and isolation of randomly distributed CNTs in an array, resulting in overlapping of individual CNTs within the array and loss of coating contiguity, and therefore, causes electrical insulation between individual CNTs.